I added a class library from one SharePoint solution to a console app. I wanted to isolate some xml mapping in class library so I could test it better without having to deploy my entire original SharePoint solution. After executing my console app, my SharePoint site collection now displays this error:

Close to nothing. It opens an xml file in a XDoc and passes it to the class library. The strange thing is, this doesn't happen on a different SharePoint environment that I have.
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Meyer DenneyAug 8 '12 at 1:11